Table 1. Main histological subtypes of fulminant myocarditis.

Subtype of fulminant myocarditis	Pathology	Incidence	Etiology	Clinical presentation/Diagnosis	Treatment
Lymphocytic myocarditis	Small mononuclear cells (CD3+ T lymphocytes)	The most frequent histological subtype	Viruses Drugs/toxins Autoimmune	Wide range of presentations The most frequent subtype in asymptomatic patients	Frequently self-limited In fulminant myocarditis, mechanical circulatory support as supportive care No clear evidence of immunosuppressants
Eosinophilic myocarditis	Eosinophilic infiltrate	Rare: unknown	Hypersensitivity (antibiotics, clozapine, carbamazepine) Churg-Strauss Hypereosinophilic syndrome Parasitic infections (Toxocara canis)	From asymptomatic to fulminant myocarditis or Loeffler cardiomyopathy Fever, skin rash if hypersensitivity Peripheral eosinophilia not always present Frequent intraventricular thrombosis	Identifying cause High-dosing corticosteroids +/− cyclophosphamide, albendazole, imatinib, azathioprine or methotrexate Mechanical circulatory support (mainly in hypersensitivity and idiopathic forms)
Giant cell myocarditis	Large multinuclear cells in the absence of well-formed granuloma Degranulated eosinophils	Uncommon	Unknown Autoimmune disorders frequently associated (25%)	Young, healthy adults Severe heart failure, refractory cardiogenic shock Frequent arrhythmic disturbances (atrioventricular block, ventricular tachycardia, ventricular fibrillation)	Aggressive, combined, immunosuppressants treatment: cardiogenic shock + cyclosporine-based treatment Rabbit anti-thymocyte immunoglobulin Muromunab, azathioprine: second-line treatment Frequent need of mechanical circulatory support
Immune checkpoints inhibitors-checkpoint myocarditis	Similar to a high-grade cardiac rejection: T cell mediated injury	Less than 1% of treated patients	Immune checkpoints inhibitors (nivolumab, pembrolizumab)	Life-threatening arrhythmic disturbances (atrioventricular block, refractory ventricular tachycardia), multiorgan failure Early presentation after initiation of immune checkpoints inhibitors (< 6 weeks) Possible other organ involvement (liver, lung, etc)	Withdrawal of the drug High dosing of corticosteroids Mechanical circulatory support